Downdraft carburetor



March 8, 1938. E. DRAHoNovsKY DOWNDRAFT CARBURETOR Filed Dec. 19, 193e 2 Sheets-Sheet yl March 8, r1938. E. DRAHONOVSKY A Haw? DOWNDRAFT CARBURE''OR Filed Deo. 19, 1936 2 Sheets-Sheet 2 imm Patented Mar. 8, 1938 UNITED STATES PATENT OFFICE 3 Claims.

pensive and efficient structure in which the auxv iliary air-admitting means is associated in a novel way with a tube, a portion of which forms a venturi.

Yet another object is to provide a novel construction in which the aforesaid auxiliary airadmitting means and tube form a single unit of the carburetor. f

With the foregoing in View, theinvention resides in the novel subject matter hereinafter described and claimed, description being accom,- plished by reference to they accompanying drawings.

Fig. 1 is a vertical sectional View through a down-draft carburetor embodying the present improvements. l

Fig. 2 is a top plan view with the cap or bonnet of the carburetor removed.

Fig. 3 is a fragmentary sectional View similar to a portion of Fig. 1 but showing the manner in which the auxiliary air is admitted at relatively high engine speeds.

Fig. 4 is a side elevation of the tube, a portion of which forms the venturi, and associated parts, in juxtaposition.

In the drawings above briefly described, a preferred construction has been illustrated and while said construction will be rather specifically explained, it is to be understood that variations may be made within the scope of the/invention as claimed.

A down-draft carburetor is shown including a body 5, a riser 6 and a cap or bonnet l, said parts 5, (i and 'I being all detachably secured together in any suitable way. The riser 6 is intendedfor connection with the usual down-draft intake manifold and contains an appropriate throttle valve 8. The neck 9 of the bonnet or 50 cap 'l is intended for engagement with the usual air cleaner and contains an appropriate choke valve I D. The body 5 includes the fuel bowl II to which the fuel is supplied in the usual way, the customary supply valve controlling-float being shown at I2. Within this body is an air (c1. esi-63) space I3 communicating at its upper end with the neck 9, said air space containing an upstanding tube I4, the main or high speed fuel nozzleY or jet I5, and the accelerating jet I6, the upper portion of said tube I4 forming a venturi I4a. The customary low speed jet is in the riser 6 and its adjusting screw is shown at I1. I

The tube I4 and the passage I8 through the riser 6, constitute a carbureted mixture passage having the venturi Ma, and the degree of subatmospheric pressure created in said venturi I41, controls the quantity of fuel discharged into the air stream' by the main or high speed jet I5. Thus, if provision be made for admitting auX- iliary air from the space I3 into the aforesaid carbureted fuel passage at relatively high engine speeds, the suction created in the venturi will be reduced, thereby reducing the amount of fuel discharged from said jet I5. Novel provision is made for attaining this end, as will now be described. I

'Ihe lower end of the tube I4 is provided with an enlarged base I9 having one portion 20 1it` ting snugly into the lower end of the air space I3 and forming a bottom for the latter and a rib portion 2| clamped between the body 5 and the riser 6. This base I9 is provided with an upwardly projecting circular wall 22 spaced outwardly from the lower portion of the tube I4, and above said wall 22, said tube is provided with a plurality of circumferentially spaced auxiliary air admission ports 23 extending from its exterior to its interior. An annular valve 24 slidably surrounds the lower portion of the tube I4, and is held in an upper position (Fig. 1) by a coiled spring 25, at relatively low engine speeds, said valve then preventing the passage of auxiliary air through the ports 23. A stop is provided to limit the upward movement of the Valve 24, said stop being preferably in the formv of a ring or flange 2S threaded upon the tube I4 and having air-conducting openings 21 from its upper to its lower side, said openings being normally closed by said valve 24. This valve is provided with a downwardly projecting wall 28 of circular form, said wall being slidably telescoped with the wall 22, providing a suction chamber 29 below the valve 24, and the base portion of the tube I4 is provided with a plurality of circumferentially spaced suction ducts 30 leading from said suction chamber 29 to the interior of the carbureted fuel passage. AAt relativelyhigh en-` gine speeds, the partial vacuuml created by the engine pistons, creates a partial Vacuum in the chamber 29 and the valve 24 therefore lowers against the action of the spring admitting air from the space I3 through the auxiliary air ports 23, to the interior of the tube I4, thereby so raising the sub-atmospheric pressure in the venturi I4a as to diminish the fuel supplied thereto from the jet I5, thereby saving on fuel consumption.

When the engine is operating at a speed for driving an automobile about twenty miles per hour, the sldable valve 24 is only partially drawn downward, the actual distance of said valve from the ring or flange 26 being then only about onesixteenth of an inch which is insuicient to placev the auxiliary air ports 23 in communication with the chamber I3. At an engine speed sufficient to drive an automobile about forty miles per hour, the valve 24 is drawn downwardly to its limit, said valve being then approximately three-eighths of an inch from the ring or flange 2B. The auxiliary air ports 23 are then in full communication with the chamber I3 to admit the auxiliary air into the tube I4. In the present structure, part of the air flowing through the ports 23, passes through the openings 21 of the ring or flange 26, and part of said air passes downwardly around the peripheral edge of said ring or flange. The auxiliary air entering the tube I4, enters below the high speed jet I5 and mixes with the gasoline and air mixture ilowing downwardly through said tube, and the auxiliary air causes a great turbulence or agitation producing a highly combustible thoroughly atomized mixture. As soon as the engine speed is reduced sufficiently, the spring 25 upwardly returns the valve 24 to its correct position, relative to engine speed.

It will be seen from the foregoing that unique means have been provided for attaining the desired'ends, but attention is again invited to the possibility of making variations within the scope of the inventionA as claimed.

I claim:-

. 1. In a down-draft carburetor, a vertical tube whose upper portion forms a venturi, said tube having an enlarged lower end providing an outwardly projecting annular base, means secured to said base andV cooperating with said tube in forming a vertical down-draft passage for air and fuel, and an air space around said tube, said base being provided with an-annular upstanding wall in'outwardly spaced concentric relation with the tube, said tube being provided with a cylindrical portion toward its lower end and with circumferentially spaced air-admission openings from the exterior to the interior of said cylindrical portion, an annular valve having an annular downwardly projecting wall, said valve slidably surrounding said cylindrical portion of said tube, said downwardly projecting annular wall being slidably telescoped with said upwardly projecting annular wall of said base, and a spring between said base and said valve Yand-normally holding said valve in a raised position in which it prevents aii` from entering said tube through said air-admission openings, the lower end of said tube having circumferentially spaced suction openings extending from theinterior of the tube to the space between the latter and said telescoped walls, whereby evacuation of air from Vthis space will occur at high engine speeds causing lowering of said valve and thereby admitting air into the tube through the aforesaid air-admission openings.

2. In a down-draft carburetor, a vertical tube whose upper portion forms a venturi, said tube having an enlarged lower end providing an outwardly projecting annular base, means secured to said base and cooperating with said tube in forming a vertical down-draft passage for air and fuel, and an air space around said tube, said base being provided with an annular upstanding wall in outwardly spaced concentric relation with the tube, said tube being provided with an annular outwardly projecting ilange above said annular wall, said ange having circumferentially spaced air admission openings from its upper to its lower side, said tube being provided with a cylindrical portion directly below said flange and with circumferentially spaced air-admission openings from the exterior of the interior of said cylindrical portion, an annular valve having an annular downwardly projecting wall, said valve slidably surrounding said cylindrical portion of said tube, said downwardly projecting annular wall being slidably telescoped with said upwardly projecting annular wall of said base, and a spring between said base and said Valve and normally holding said valve in a raised position in which it abuts said annular flange to prevent entrance of air into the tube through said air-admission openings of said ilange and tube, the lower end of said tube having circumferentially spaced suction openings extending from the interior of the tube to the space between the latter and said telescoped walls, whereby evacuation of air fromv this space will occur at high engine speeds causing lowering of said valveand thereby admitting air into the tube through the aforesaid air-admission openings.

3. In a down-draft carburetona vertical tube whose upper portion forms a Venturi, said tube having an enlarged lower end providing an out wardly projecting annular base, carburetor sections secured against the upper and lower sides of said base and cooperating with said tube in forming a vertical down-draft passage for air and fuel, and an air space around said tube, said base being provided with an annular upstanding wall in outwardly spaced concentric relation with the tube, said tube being provided with an annular outwardly projecting flange above said annular wall, said flange having circumferentially spaced air admission openings from its upper to its lower side, said tube being provided with a cylindrical portion directly below said flange and with circumierentially spaced air-admission openings from the exterior to the interior of said cylindrical portion, an annular valve having an annular downwardly projecting wall, said valve slidably surrounding said cylindrical portion of said tube, said downwardly projecting annular wall being slidably telescoped with said upwardly projecting annular wall of said base, and a spring between said base and said valve and normally holding said valve in a raised position in which it abuts said annular flange to prevent entrance of air into the tube through said air-admission openings of said flange and tube, the lower end of said tube having circumferentially spaced suction openings extending from the interior of the tube to the Vspace between the latter and said telescoped walls, whereby evacuation of air from this space willoccur at high engine speeds causing lowering of said valve and thereby admitting air into the tube through the aforesaid air-admission openings.

EUGENE DRAHONOVSKY. 

